1. Field of the Invention
The present invention relates generally to medical devices, and more particularly to endoluminal delivery systems for prostheses such as stents, or other implantable structures. The delivery systems may be used for placement of a stent in the arterial system, the venous system, or any other portion of the body. The use of stents and other implantable medical devices such as grafts, stent-grafts, filters, shunts, valves, etc., are referred to herein as prostheses. Prostheses may be used to deliver drugs to tissue, support tissue, or maintain patency of bodily lumens, as well as performing other functions, and have been widely reported in the scientific and patent literature.
Stents are typically delivered via a catheter in an unexpanded configuration to a desired location in the body. The combined stent and catheter is typically referred to as the stent delivery system. Once at the desired location, the stent is expanded and implanted into the body lumen. Examples of locations in the body include, but are not limited to, arteries (e.g. aorta, coronary, carotid, cranial, iliac, femoral, etc.), veins (e.g. vena cava, jugular, iliac, femoral, hepatic, subclavian, brachiocephalic, azygous, cranial, etc.), as well as other locations including the esophagus, biliary duct, trachea, bronchials, duodenum, colon, and ureter.
Typically, a stent will have an unexpanded configuration with reduced diameter for placement and an expanded configuration with expanded diameter after placement in the vessel, duct, or tract. Some stents are self-expanding, and some stents are mechanically expanded with a radial outward force applied from within the stent (e.g. with a balloon). Some stents have one or more characteristics common to both self-expanding and mechanically expandable stents.
Self-expanding stents are made from a material that is resiliently biased to return to a pre-set shape. These materials may include superelastic and shape memory materials that can expand to an implanted configuration upon delivery or through a change in temperature. Self-expanding stents are constructed from a wide variety of materials including nitinol (a nickel titanium alloy), spring steel, shape-memory polymers, etc.
In many stent delivery systems, particularly those used to deliver a self-expanding stent, the stent is typically retained on the catheter in its unexpanded form with a constraining member or other retention device such as a sheath or outer shaft. The stent may be deployed by retracting the outer shaft from over the stent. To prevent the stent from being drawn longitudinally with the retracting shaft, many delivery systems provide the catheter shaft with a pusher, bumper, hub, holder or other stopping element.
Precise delivery of stents can be challenging. In the case of balloon expandable stents, the stent may foreshorten as the stent radially expands, therefore, the change in length must be taken into account when deploying the stent at the treatment site. In the case of self-expanding stents, due to the elastic nature of the stents, they may “jump” away from the delivery catheter during deployment. For this reason, it would be desirable to provide improved stent delivery systems that can accurately deliver a prosthesis such as a stent to a desired treatment site. Additionally, depending on the anatomy being treated, this may add further challenges to accurate stent delivery. In certain parts of the anatomy, exact placement of the stent is critical to the successful clinical outcome of the procedure. For example, percutaneous coronary intervention (PCI) in ostial coronary artery lesions has been technically difficult because the stent is preferably precisely deployed in the ostium without side branch compromise. A similar level of accuracy is needed with ilio-femoral and ilio-caval stenting as is routinely used for the treatment of iliac vein compression syndrome (IVCS) and post-thrombotic syndrome (PTS) whereby the profunda and the inferior vena cava can be partially or completely blocked (or “stent jailed”) by the stent if the stent is not placed accurately after deployment. Other examples where precise placement of the stent are important include but are not limited to any number of arterial applications, esophageal stenting of gastric varices, transjugular intrahepatic portosystemic shunt (TIPS) stenting for relief of portal hypertension, and use of endovascular stent-grafts for arterial aneurysms (e.g. AAA, femoral, popliteal).
Additionally, depending on the direction from which the delivery catheter approaches the treatment site, it may be desirable to deploy the stent in a preferred direction. Physicians may enter the body through different access sites, e.g. femoral vein or artery, the internal jugular vein (UV), etc. before inserting the stent delivery system through the bodily lumens to the target location. Because the stent delivery system will be in different orientations depending on the physician's choice for access site, it may be necessary for the delivery system to have the correct stent release mode, such as proximal or distal release of the stent. It would therefore be advantageous for a delivery system to allow both release modes such that the operator (e.g. physician), can use the same system with either approach. With the typical commercially available stent delivery system, the operator is limited to one approach due to the distal release of the stent. Physician technique in stenting can also dictate which release is used in a procedure. For example, in the case of iliofemoral stenting with a femoral approach the user may choose to deploy and overlap multiple stents of varying sizes using proximal release such that the smaller diameter stent is placed first and the amount of overlap with the secondary stent(s) is tightly controlled.
In situations where multiple stents are delivered, it may be desirable to selectively deploy the stents. For example, abdominal aortic aneurysm (AAA) stent-grafts can be constructed of multiple components—trunk or main body, bifurcated main, main extension, limb extensions, stepped limbs, flared limbs, etc. Because each component is placed and deployed with a preferred release, one bi-directional deployment system with multiple stents, or stent grafts, or components could serve the function of numerous standard delivery systems. The deployment of the stents or components can be any combination of proximal or distal releases. This type of stenting can be useful in other areas of the body where bifurcations are present as well.
Furthermore, operators may require bi-directional deployment in cases where the target location is bookended by anatomical features that require exact stent placement of both the distal and proximal ends of the stent. Two bi-directional deployment systems may be used with one employing the distal release and the other employing the proximal release. The non-critical ends of each of the deployed stents would overlap with each other in the middle of the target location. Without bi-directional deployment capability, an operator would face the likelihood of understenting, overstenting, or inaccurate stent placement and suboptimal results because of the inexact lengths of stent available to treat an exact length of disease. As mentioned earlier, ilio-femoral and ilio-caval stenting of the venous system may require the user to stent entirely from the confluence of the inferior vena cava to the profunda of the leg. A distal release is preferred for accurate stent deployment at the confluence, whereas a proximal release is preferred so as to avoid “stent jailing” of the profunda. In lieu of performing this procedure with two bi-directional deployment systems, another bi-directional deployment device embodiment loaded with two stents (one deployable with distal release and one deployable with proximal release) could greatly simplify this type of procedure.
Therefore, it would be desirable to deploy a stent from its distal end toward its proximal end, as is traditionally done in many conventional stent procedures. In other cases, it would be desirable if the stent could be deployed from its proximal end toward its distal end. In the case where multiple stents are deployed, it would be desirable if a first stent could be deployed in a first direction, and a second stent deployed in a second direction that may be the same or different than the first direction. Thus, improved stent delivery systems such as a bi-directional stent deployment system, also referred to as bi-modal, or selectively deployable stent delivery system would be advantageous. Additionally, since there currently are no FDA approved and commercially available stents and delivery systems for treating venous outflow obstruction, there is need for such devices and methods of use. At least some of these objectives will be met by the inventions described herein.
2. Description of the Background Art
Relevant patent applications include U.S. patent application Ser. No. 12/903,056, filed Oct. 12, 2010, the entire contents of which are incorporated herein by reference. Other relevant patents and publications include U.S. Pat. Nos. 7,137,993; 6,849,084; 6,716,238; 6,562064; 5,873,907; and U.S. Patent Publication Nos. 2009/0264978; 2004/220585; 2002/120323; and 2002/188341.